Exotoxins and Endotoxins and Difference between Exotoxins and Endotoxins

Tankeshwar Acharya

5 years ago

Exotoxins:

Definition: Toxins that are released extracellularly as the organism grows are called exotoxins. Exotoxins may travel from a focus of infection to distant part of the body and cause damage. E.g. Neurotoxin (botulinum toxin, tetanus toxin), Enterotoxin (cholera toxin), Cytotoxin

Endotoxins:

Definition: Endotoxins are lipopolysaccharides toxin produced by Gram negative bacteria. The name endotoxin is derived from the fact that these toxins are generally cell bound and released only when the cell lyses.

Basic properties and differences between Exotoxins and Endotoxins

Property

Exotoxins

Endotoxins

Biomolecule/Chemistry

Proteins

Lipopolysaccharide-Lipoprotein complex

Location of genes

Plasmid or bacteriophage

Bacterial chromosome

Source

Excreted by certain gram positive or gram negative bacteria

Cell wall of Gram Negative bacteria, released only after lysis of cells

Heat Stability

Destroyed rapidly at 60oC (except staphylococcal enterotoxin)

Stable at 100oC for one hour

Mode of Action (Symptoms)

Specific. Either cytotoxin, enterotoxin or neurotoxin with defined action on cells or tissues

General. fever, diarrhea, vomiting

Toxicity

Highly toxic, often fatal (fatal dose on the order of 1 µg)

Weakly toxic, rarely fatal (fatal dose on the order of hundreds of micrograms)

Immunogenicity

Highly immunogenic, stimulate the production of neutralizing antibody (antitoxins)

Relatively poor immunogenicity

Toxoid potential/Vaccines

Treatment of toxin with formaldehyde will destroy toxicity, but treated toxins remain immunogenic.
Toxids used as vaccines